In recent years, a large amount of data have been handled by computers along with the advent of advanced information society, and many computers have been installed and collectively managed in a single room in many cases. For example, in a data center, many racks (server racks) are installed in a computer room and each rack houses a plurality of computers (servers). Then, jobs are organically distributed to the computers and a large amount of jobs are efficiently processed.
In a data center, a large amount of heat (waste heat) is generated along with operation of computers. Conventionally, the heat is emitted to the atmosphere. However, in view of energy conservation and environmental loading reduction, a proposal has been made to recover and reuse the heat. Accordingly, attention has been focused on an adsorption heat pump as an apparatus which recovers and reuses heat at a relatively low temperature.
An adsorption heat pump includes, for example, an evaporator, two adsorbent heat exchangers, and a condenser. In the adsorption heat pump, the temperature of water flowing through a tube in the evaporator is reduced by utilizing an action of a refrigerant such as water or methanol which removes heat from the surroundings when being turned into vapor. The refrigerant vaporized in this process is adsorbed to an adsorbent placed in each of the adsorbent heat exchangers.
While one of the adsorbent heat exchangers is used for adsorption of the refrigerant, the other adsorbent heat exchanger performs recovery (drying) of the adsorbent. In the adsorbent heat exchanger on the recovery side, the adsorbent is heated by feeding hot water with a temperature increased by waste heat into the adsorbent heat exchanger, and thereby the refrigerant is evaporated. The vapor of the refrigerant desorbed from the adsorbent is cooled and returned into liquid by the condenser, and then the refrigerant is transferred to the evaporator.
In the adsorption heat pump, the adsorbent heat exchanger used for adsorption of the refrigerant and the adsorbent heat exchanger used for recovery of the adsorbent are switched at regular intervals.    Patent Document 1: Japanese Laid-open Patent Publication No. 2000-35256    Patent Document 2: Japanese Laid-open Patent Publication No. 2003-114067
For the purpose of further promoting energy conservation and environmental loading reduction, additional improvement in thermal efficiency of an adsorption heat pump is desired.